Typically, the mixing angle \(\theta \sim 10^{-6}\)  is predicted by the seesaw relation with \(m_\nu \sim 0.1\)  eV and \(m_N\sim 100\)  GeV. Such a small mixing angle is beyond the reach of future colliders[1]}. In this paper, we take \(\theta \)  as a free parameter. Large mixing angle is possible in low scale models, such as inverse seesaw [2]}, [3]} and linear seesaw [4]}, [5]}, [6]}.
